Means for intensifying the directional characteristic of directive antenne



Sept. 5, 1933- w. VAN B. ROBERTS 1,925,570

MEANS FOR INTENSIFYING THE. DIRECTIONAL CHARACTERISTIC 0F DIRECTIVEANTENNJE Filed March 8, 1929 SCREEN 6H0 'l l M 100/ 21.5 1 9 415 3aavwwwoz WALTER VAN B. ROBERTS his Gl tter/M45 Patented Sept. 5, 1933 UNl'lED STATES,

* PATENT; OFFICE MEANS FOR INTENSIFYING THE DIREC- TIONAL CHARACTERISTICF DIRECTIVE 'ANTENNEE Walter van B. Roberts, Princeton; N. J., asaSignor .to Radio Corporation of America, a cor--.

poration of Delaware Application March' 8,f1929. Serial No. 345,424 .4Claims. (01. 250-11) This invention relates toreceiving apparatus to beused with any type of directional antenna and in particular withdirectional antenna of that typefwhich utilizes afrotatable closedinductance to pick up signal voltage.

Directional receivers in general use today, usually include a radiantenergy pickup device of the above type for obtaining the direction ofthe signalsource, means for associating the.

1 signal voltage received inl'said inductance with receiving apparatuswhich usually includes a detector and an aural indicating device, and'means' for introducing into the pickup device or receiver input avertical aerial component to j-iobtaina sense of direction in thereceiver output. i r

. Usually, in apparatus of this typ when the signal voltage pickupdevice is rotated to such a-position that-its planefis' at right anglesto i the source of signal voltage, the output of the detector asindicated in the indicatingdevice is i at minimum while, when the signalvoltage pickup device is; rotated to aposition such that its plane is inthe line of the signalenergy the output of the receiving apparatusfassociated therewith is maximum: in some instances the position of thepickup device which gives maxi mum response in the indicating device isused to determine the direction of the source of ra i diant energy whilein other instances the position' of the pickup device which givesminimum response isyutilized to obtain the direction of the source ofenergy. In either case the greater the change in the output of thereceiver per. degree departure of the signal voltage pickupdevice fromthe position giving'maximum orminithe receiving apparatusfasscciatedwith the loop,

antennalikewise varies but little over; afconsiderable'angular variationof the" loop' about the truemaximum pointing. position of the loop.Likewise when the point" of zero response is utilized to ascertain thedirection 1 of f the sig:

nal voltage source the signal voltage in the loop' and the response inthe output increases but a small amount when the loop is rotated,through a considerable angle in either direction from the position atwhich no signal voltage is induced in theloop'.

Briefly and broadly the object of this invention is to provide means forcausing a greater percentage change in the detector output of thereceiver associated'with the signal voltage pickup device than is causedin the signa'lvoltage induced in the'pickup device when it is orientedfrom the true pointing position. j

Another'object of this invention is to provide a device of the'above'character which can be utilized withoutalteration in the receiver or inthe pickup device with all directional aerial pickupdevices of any typeknown at present. This is accomplished by the use of. novel ap'-'paratus interposed between 'the signal voltage pipkup'device, andtheindicating device which willgreatly increase the percentage of changein response in the indicating device with respect to the percentageoffchange of voltage in the directional antenna. 1 I

According to this invention the signal energy from the pickup device isamplifiedthe required amount, passed through'a succession offrequencyidoublers and then fed to the input circuitof the detector. Inthis manner due to the fact that the output voltage of a frequencydoubler is substantially proportional to the square of the amplitude ofthe'impressed' oscillations the final outputofthe detector which in turnamplifies as the square of the impressed voltage'iwill be proportionaltoa high power of the voltage induced infthe loop circuit and impressedon' the-input elements of the first tube:

The exact :power-to'which the voltage is raised is determinedbythenumber of frequency doublers employed. Obviously this will result in avery great diminution in detector output voltage when the loop isremoved. irom the position of maximumfresponse'a very slight amount orwill result in avery great increase of detector out-.

put voltage when the loop is moved a slight amount from position of zeroor minimum re-' sponse. i

A' better understanding of the invention'will be hadfrom the followingdetailed description andtherefore when read in connection with theattached drawing throughout which like reference characters indicatelike parts and in which;

Figure 1 shows diagrammatically an arrangement of a receiver constructedin accordance with my invention;

' while In Figure 2 which showsa-circuitdiagram of.

the apparatus shown diagrammatically in Figure 1 the energy isv pickedup by means-of r tatable loop 1 tuned to the signal frequencyby means ofa variable condenser2. i This energy is fed to the input-'elements ii; iofa thermionic four element amplifier tube 5. The i-proper amount ofamplificationin this tube is assured by maintainingthegri'd electrode 3'of the tube 5 at the proper potential bymeans of a biasing battery 6. Anoutput circuit having an inductan'ce 7j-and source of power 8;isconnected be:

tween the output elementsofjth'e thermionic tube 5. Reaction betwteentheoutput andinput circuits -of ,the,- amplifier stage is prevented I byusing atube of that type in which a fourth shield element 9' is providedbetween the grid and plate "electrodes; This electrode also servespreselected. point on. the, plate potential battery the .purpose of avariable volume control the amount of volume! depending on the positionofthe tap to which the electrodeis'connected on'the'potentiometer 10connected between a 8 and the negative terminal of the filament."

thermionicvtub'e e is coupled toan inductance 11..i n the inputgcircuit'of thermionic tube 12. This'input ci'r 'uitis'tuned by means of ajcomdenser 31 tov the fundamental frequency. In order that tube ;.12 act asan,eff1 cient f requency doubler the proper potential is applied to thegrid electrode thereof by means of a 12 is closely cnupledbymeans of an.inductance 14 therein to enmductanm 1 5,in the input circuit ofatherrnionic'..tube 16. I Potential is applied to the anode of. tube 12by,;means of a source .of. poweril 7 connected betweenfthe an ode andcathode of tube.l2. The inputgcirizuit of tube 16"is tuned'by vmains ofvariable'condenser to double the frequency. of the in-' comingflsignal.This" stage. as? a result produces roscillationsiinthe output 'cifcuitof tube 12 and consequently 1'n.] the input lcircuifof tube 16 whichvary. as the square of the r scilIatiOns set up in the input circuit of,tub12." i i v The output circuitl of thermionicf tubefllfi f?whichincludes .indiictancelS and powerf source 19 is closely coupledbymeans of inductance 18jto an inductancef20 in the input circuit of athermionic tube 21. In order that tube 160p;

erate as an efiicient frequency doubler a biasing T battery 22 isprovided to'maintain the grid electrode' thereof at thepropezi'po'tential. The in,- put circuitof tube, 2lis tuned by means ofa variable condenser'23 in shunt with the in-v ductance'20 to afrequency twic'ethe frequency 5 of the preceding tuned circuit 14,15;In'other words the frequency of the'tuned"circuit'20, 23

This amplifier may or rnay The amplified of the .first voltage.

of frequency doublers have been shown it will be understood that thenumber of stages may is four times the frequency of the signal to bereceived. Thermionic tube 21 is operated as a chic tube operating as adetector are substan- Ttially proportional to the square of theamplitude of the voltage oscillations in the input cir cuit. thereof.Consequently when two stages operating as. frequency doublers are usedthe amplitude ofthe voltage oscillations in the output circuit thereofare substantially proportional to age oscillations impressed on theinput circuit An indicating apparatus, as for instance, a'loudspeaker Tis connected in the output circuit of the thermionic tube 21.

As will be readily seen when a receiver constructed in accordancewiththe present invention is used with "any known directional aerialsystem, a small movement of the pickup device from position ofmaximumresponse will result in a great decrease .in, signal strengthinthe indicator'l; or in case the point of zero response is being used asmall movement of the pickup devicefrom position of zero response in'the indicator will result in a great increase in signal strengththerein, The true-direction of the source of energy can be readily foundwith my receiver associated with any known aerial system. f j While, forpurposes of illustration, two stages be increased or decreased the exactnumberin each instance depending on the degree of am plification andconsequently pointing accuracy V I required without departing from thespiritof @Ihe inductance '7 in theoutput circuit of, a

the invention. V InFigure 3 iS'fihOWIl an arrangement which.

differs from Figure 1 'in that this modification utilizes the well knownheterodyne or beat method of receptionJ In this arrangement which isotherwise similar to Figure 2 a beat frequency is produced in the outputcircuit 27 -28 of a thermionic tube M which serves as a frequencychanger by means of an oscillation generator 25 coupled'to an inductance26 inthe input circuit 1-2 of said tube thecontrol'electrode of Mismaintained at the proper potentialby means of a battery 29. Inductance2'1 in the output circuitof 'M is closely coupled to inductance 1a inthe input circuit of therinionic tube 5 which operates similar tothermionic tube 5 of Figure 2. The number of tuning controls required inthe modificationshown in Figue 2. is materially reduced by utilizingthis method since the second, third and fourth stages may consist ofintermediate frequency this case as in the preceding case the number ofintermediate: stages may be increased or devention and the operationthereof it will be' understood that I do not wish to limit myselfthereby except as marked out in the claims appended hereto.

I claim:

1. In radio apparatus a rotatable directive aerial, an amplifier havingan input circuit associated therewith, a. frequency doubler stage havingits input circuit associatedwith the output circuit of said amplifierand rectifying apparatus operatively associated with said frequencydoubler. I

2. In a rotatable frame receiver, a directive aerial, a plurality ofcascade amplifier stages connected to said aerial, a plurality-ofcascade stages of frequency doublers associated with the output of saidamplifier, and a rectifier asso-- ciated associated with the output ofsaid frequency doublers, V

3. Radio apparatus comprising the combination of aloop aerial tuned tosignal frequency,

a thermionic tube having input elements connected to said'loop' aerial,means for producing oscillations at a frequency difiering from thesignal fequency by an intermediate frequency, means for coupling saidlast named means to said loop circuit, an amplifier tuned to theintermediate frequency coupled to the output circuit of ,said tube, aplurality of frequency doublers associated with said amplifier anddetecting apparatus associated with said frequency doublers.

4. In combination, a directional antenna system of adjustabledirectivity, a local oscillator, means connected with said antennasystem and said oscillator for amplifying a fixed frequency produced bycombining said' local oscillator with signal frequencies picked up bysaid antenna, a non-linear space discharge device, means for impressingsaid amplified fixed frequency voltage on said non-linear spacedischarge device, means for selecting from the output of said spacedischarge device a frequency which is a multiple of said fixedfrequency, and indicat- 1 ing means operated by said multiple frequency.

WALTER VAN B. ROBERTS.

Patent No. 1,925, 570. Segatember 5, i933.

VAUTER van RGBERTS.

it is hereby certified iiiat errez simmers in the printed speeiiieaiien0i the abm e numbered patent requiring een'eetien 21s ieiiews: Page i,iiie if}, fer "pipime read pickup; page 3, iine i9, eieim 2, im"mtate'bie ii'ame" read directive mad for "directive" read reiatabieframe; and line 24, strike mat the werei "associated"; and that ihe saidLetters Fatent should ee read with these cen'eetions therein that thesame may eeniorm to the record of time ease in the iatent Office.

Signed and sealed this 13th day ei March, A. D. 193

F. M Hopkins (S ai) Acting Gammissiener of Patents.

CERTEFICATE 0F GQRREQTION.

Patent Ne. 1,925,570. September 5, 1933.

WALTER van B. ROBERTS.

it is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 1,line 76, for "piphup" read pickup; page 3, line 19, claim 2, for"rotatable frame" read directive and for "directive" read retatabieframe; and line 24, strike out the word "assoeiated"; and that the saidLetters Patent should he read with these corrections therein that thesame may conform to the record of the case in the Patent Office.

Signed and sealed this 13th day of March, A. D. 1934.

F. M. Hopkins (Seal) Acting Commissioner of Patents.

